A Visit to the Snowman

On 18 November 2010, NASA announced that two craters photographed in early November by the Mars Exploration Rover Opportunity during its drive toward Endeavour Crater have been named in honor of the Apollo 12 CSM, Yankee Clipper, and LM, Intrepid. The names were suggested by MER science team member, James Rice, NASA Goddard. Yankee Clipper Crater (0.2 Mb anaglyph) is about 10 meters across while Intrepid Crater (0.6 Mb color) is about 20 meters across. Intrepid is similar in size and appearance to Eagle Crater (0.5 Mb anaglyph), where Opportunity came to rest on Mars on 25 January 2004.

[NASA photo 108-KSC-369C-317/8 is a characteristically-irreverent portrait of the All-Navy crew of Apollo 12, taken on 22 October 1969. From top to bottom, the photo shows Lunar Module Pilot (LMP) Al Bean, Command Module Pilot (CMP) Dick Gordon, and Mission Commander (CDR) Pete Conrad. We pick up the mission just before the Command Module Yankee Clipper and, shortly thereafter, the Lunar Module Intrepid emerge from behind the Moon on their 14th orbit. This event is called Acquisition of Signal or AOS. The Flight Director is Cliff Charlesworth and the CapCom is Astronaut Jerry Carr. The tape, recorded in Houston, has a fair bit of static. NASA's Public Affairs Office (PAO) commentator mentions that Armstrong, Aldrin, and Borman are in the Mission Operations Control Room (MOCR).]

109:41:25 MP3 Audio Clip (Houston) (1 min 42 sec)
[The late Bernie Scrivener recorded a pair of 4-track tapes at Honeysuckle Creek during Apollo 12. After Bernie's death, Rosemary, his widow, passed the tapes on to Mike Dinn, Deputy Director at Honeysuckle during Apollo, who digitized the recordings in MP3 format and provided the files to A12FJ editors Lennie Waugh and David Woods. The time is currently 0603 UTC on 19 November 1969. The Moon rose at Honeysuckle Creek about two hours ago. For sections covering times when spacecraft comm was being received at Honeysuckle, the Scrivener recordings are of higher quality.

[The following dialog is taken from the raw, on-board transcript ( 10 Mb PDF ). They are about a minute and a half from Acquisition-of-Signal from Houston.]

109:42:07 Bean (on-board): Check off the good things I did. You did. We did.

109:42:10 Conrad (on-board): All right. COAS is to the overhead window; DOI postburn report we'll get; helmets and gloves are on; Cabin Repress (cicuit breaker) is Closed, Suit Gas Diverter (valve) to Egress; Egress; Cabin Reg(ulators) A and B, Egress; and we're standing by for the Updata Link switch. We're going to get earthrise in just a second. You ought to have earthrise by now, Dick.

109:42:34 Gordon (on-board): (Garbled) be a while yet because I'm looking backwards.

109:42:39 Conrad (on-board): Oh, that's right. I forgot. (Pause) It's going to be about 109:43:30. It's going to be right straight out there or what, I wonder? I'm kind of guessing it is.

109:43:02 Bean (on-board): Or maybe, would it ...

109:43:03 Conrad (on-board): Yes.

109:43:04 Bean: (on-board) ... maybe the 15-degree inclination's going to do something to it. I just always imagined it was right in front of us.

[Although Pete and Al have not yet seen Earthrise, Houston has just had acquisition of Signal (AOS) from the Command Module, which is in a different orbit. Houston won't receive Disk's next transmission until 109:43:56.]

109:43:17 Carr: Yankee Clipper, Houston. How do you read? (No answer) Yankee Clipper, Houston. How do you read? (Long Pause)

109:43:33 Bean (on-board): Starting ...

109:43:34 Conrad (on-board): There it is! Look at it! Goldarn! Watch it ... just ... keep ... Just click them (meaning Hasselblad photos) off. Oh, that is fanstastic!

[Pete and Al have just seen Earthrise. Al is taking a series of photos out his window. The frames are AS12-47-6879 to 6895. Journal Contributor GoneToPlaid has created an 8-minute animation (136 Mb) presenting the images and using Celestia to determine the approximate longitude/latitude/altitude from which each frame was taken. The animation is also avialable on YouTube.]

[Bean - "As I remember, the static occurred when you weren't locked up yet. And, when you got the S-Band locked up..."]

[Conrad - "I also don't think we got too much static on board."]

[Bean - "I don't either. But you could tell when we were locked up."]

[Conrad - "Yeah; but this is a ground recording. And I don't think we noticed much static. And I also remember getting trapped very badly in Skylab because I would never know when the ground was listening."]

[Bean - "And, here, you did. You knew when you finally got it; and then you'd hear the words."]

109:43:56 Gordon: Houston, Clipper.

109:43:58 Carr: Roger, Clipper; Houston. Loud and clear.

109:43:58 Conrad (on-board): Give them high gain, Al.

109:44:01 Bean (on-board): They haven't got us yet, Pete.

109:44:02 Conrad (on-board): Oh, okay.

109:44:03 Bean (on-board): But I'll go over on it and we'll make it ...

[Gordon is reporting that, at about the midpoint of the Farside portion of the orbit, there had been a successful burn of the Lunar Module Descent engine, putting Conrad and Bean on a trajectory with a low point about 50,000 feet above the lunar surface. Shortly before they reach that low point, they will begin the powered descent to the surface.]

109:44:09 Conrad (on-board): You can get some more pictures if you want.

109:44:11 Bean (on-board): I'm getting them right now.

109:44:13 Conrad (on-board): God dog!

[If this transcription is correct, Pete was so excited that he momentarily forgot to clean up his use of profanity and had 'God damn' half out before adding the second half of 'Hot dog'.]

109:44:16 Bean (on-board): Tell them about it, babe. (Pause) f:11, (One) 250(th of a second) is what we've been using, isn't it, Pete?

109:44:23 Conrad (on-board): Yes, yes.

109:44:16 Bean (on-board): That's got to be so fantastic.

109:44:30 Carr: Intrepid, Houston. How do you read?

109:44:33 Conrad: Hello, Houston; Intrepid. Roger. We read you loud and clear, and we just watched our first Earthrise, which was fantastic! And we had a great DOI (Descent Orbit Insertion) burn. The X residual was 0; Y was plus two tenths (0.2); and Z was minus six tenths (-0.6).

[These are three-axis velocity residuals (in feet per second) given by the Primary Guidance and Navigation System or PGNS (pronounced 'Pings'). Pete is reading the numbers on the computer's display and keyboard panel (DSKY).]

[The Abort Guidance System - or AGS - is the backup navigation system designed primarily to get the crew back to orbit in an emergency. Shortly, they will re-initialize the AGS so that it will start the descent in agreement with the PGNS.]

[Bean - "The AGS had strapped-down gyros and it integrated them. And the PGNS had a whole inertial platform with accelerometers on there."]

[David Woods has provided scans of pages 15 (1.0Mb) and 16 (1.0Mb) from the Apollo 15 Lunar Module Cue Cards, which cover various abort scenarios. On page 16, for a return to orbit using either the descent engine (lefthand column) or the ascent engine (righthand column). The Commander would check the position of the Guidance Switch and then push either the Abort button or the Abort Stage button, respectively. Illustration by Thomas Schwagmeier.]

109:45:18 Conrad: Coming at you; (wait) 1 second.

109:45:27 Bean: AGS residuals were plus 0.3, plus 0.1, and minus 0.6.

[The close agreement between the PGNS and the AGS is a sign both of a good burn and of satisfactory performance by both navigation systems.]

[Comm Break. Both spacecraft are equipped with low-gain, omni-directional antennas and with high-gain antennas that require accurate pointing at Earth. The omnis can handle only a relatively modest rate of data transmission. Now that the high-gain antenna is locked on Earth, they can switch to high-bit rate.]

109:46:12 Bean (on-board): Don't lose that picture. That's going to be one that's going to hang around for years. I don't give a shit if it's ... streaked. (Long Pause)

[The raw transcript attributes the transmission at 109:46:12 to Al. Journal Contributor Thomas Schwagmeier suggests that, because Al was using the Hasselblad, the speaker is actually Pete. I agree, in part because the phrasing and word choices are pure Pete. A digitization of the on-board, when it becomes available, will answer the question.]

109:46:35 Conrad (on-board): Okay, I'm going to go ahead and get my... No, I'll wait ... until I get the computer.

[Bean - "That's right. They could get the state vector and things like that."]

[Journal Contributor Frank O'Brien notes, "Program 00 (P00) is really not a program at all, but rather, puts the computer in an 'idle' state. This ensures that there is no other processing that might change the values being sent up by Houston. Here, one of the two VHF communications systems was configured to send either voice, or data to the computer. By placing the switch in the 'Data' position, they are allowing Houston to input a new state vector which is, essentially, the current LM location and three-axis velocity."]

[O'Brien continues: "It's best to use a modern example to explain how P00 operated in the Apollo Guidance Computer (AGC). In a modern PC running Windows 95 for example, where you haven't started the word processor, E-mail or any other application, you think of the machine as 'idle'. This is usually synonymous with the idea that no 'work' being done. In reality the processor is ALWAYS running, full blast. What is it doing? First, it is simply checking to see if there is any new work to be done. No work, go around and check again. The idea that a computer 'sleeps' while waiting for work is a bit of a misnomer. It is usually in a very small loop that is easy to interrupt when something useful comes along."]

["This is the conventional description of an 'idle' computer; but is it really 'idle' when there are no programs running? Probably not. There are also several 'background' programs running; the print spooler, networking software, resource managers, etc. These are going and doing critical work, even though you don't think of having a 'program' running. On a large system, such as a big UNIX system or the traditional IBM mainframe, there can be several dozen of these background programs running."]

["Now, let's return to the AGC. It only had the ability to run one 'program' at once (much like MS-DOS). P52 IMU alignment, P12 LM Ascent, P63 LM Descent are the examples of what we think of as AGC 'programs'. But even when these 'programs' are not running, there is a lot of work that has to be done. Most importantly, integrating the state vector (every two seconds), and Digital Autopilot (DAP) tasks (every 1/10 of a second) are examples of functions that must be performed continuously, regardless of what program is running."]

["It is interesting to note that because there are so many 'programs' active in the AGC at any one time, it's more correct to talk about which 'Major Mode' is active. Yes, in casual references and even in much of the documentation the word 'program' is used when referring to P64. However, the formal phrase, 'Major Mode' is a better reflection of how the computer is architected: Several programs running, but only one Major Mode."]

109:48:04 Bean (on-board): Coming over to AC and I'm going to Inverter 1. I've got it. Okay. See that guard? That's a - that's a bad one, boy. You could flip that out so easy. I've been worried about that one for months.

[Journal Contributor Paul Fjeld believes that Al is referring to the three-position Inverter Switch on Panel 14, shown in a detail from a photo taken during the LM-6 close-out. " Looking at the inverter switch guard, each side has what looks like a plastic cover with some funky toothed edging on both sides which might snag and then pull off the metal base?" Paul notes that the switch, itself, was "just one of those standard pull-out/then-set types."]

[Houston wants to monitor Pete's heart during the descent. The Commander's station is on the left side of the cabin, hence the request for the 'left' setting of the selector. Al is wearing biomedical sensors, but the LM systems are only set up to allow the surgeons to look at one crewman at a time.]

109:48:54 Conrad: Okay. Going Biomed, Left. (Long Pause)

109:48:56 Bean (on-board): Had a feeling they were going to want that.

[Bean - "We sound real stuffy in the head compared with how we talk here (on Earth). Which is just the way we always did in space. But I notice it here a lot."]

[Al had taken an Actifed, a decongestant tablet, before donning his helmet.]

[Bean - "Yeah, because we did have a stuffy head. We didn't know then that you always do and we were all taking medicine that we shouldn't have been taking. See, now we know that you always have stuffy heads in zero-g. Sort of like when Frank Borman got sick and threw up on Apollo 8 and didn't say much about it. He thought it was a bug (that is, a viral infection). Now we think it was motion sickness because so many people got motion sickness and never showed any bug signs later. And it fit(s) the way motion sickness works."]

109:49:11 Conrad: How soon before you're going to send up the data, Houston?

109:49:16 Bean (on-board): Throttle, Min.

109:49:17 Conrad (on-board): Min.

109:49:18 Carr: About one minute, Pete.

109:49:21 Conrad: Okay. I'll hold then. We're standing right by to do the mode-2 lock on the radar, so we're holding.

109:49:26 Carr: Okay ...

[They are going to track the Command Module with the rendezvous radar (LM-9 photo by Randy Attwood) in order to make sure that the radar is working properly and to estimate what their altitude will be at Powered Descent Initiation (PDI). They will also use VHF ranging - basically a Doppler measurement - to determine their radial velocity relative to the Command Module.]

[Dick is currently on Rev 14. Carr is going to read up the times of his next LOS, the start of Rev 15, and his Rev 15 AOS.]

[In response to a question about the term "map update", David Woods writes "I think this usage did derive directly from reference to a physical map but that its usage evolved over the programme. On Apollo 8, map updates included things like the time they would pass over a particular meridian. An example can be found at 070:32:55 in the Apollo 8 Flight Journal. Later, the map update tended towards merely a note of LOS, start of rev (which would be near the 180 meridian) and AOS. One advantage of this is it allows the crew to synchronise time with their groundtrack. With a rev taking essentially 2 hours, then every half hour represents 90 degrees of revolution and knowing when they fly over the 180 meridian helps them keep track of what territory they subsequently fly over."]

109:50:52 Conrad: We got it (in) P00 and Data for you. (To Al, telling him to set the switch to Data) Go ahead.

[The switch is at the lower left on Panel 12, which is on Al's side of the cabin. The Updata Link switch has three positions: Voice B(ack)U(p), Off, and Data. Illustration by Thoams Schawgmeier.]

[Conrad - "They could not update anything without us allowing them. I remember arguing with Flight Ops for months over that in the early days. I said, 'I'm not going to let you mess around with the computer without us knowing about it.'"]

[For the descent, they are wearing their suits, helmets, and gloves - albeit unpressurized. The gloves are the Intravehicular (IV) gloves which consist of the pressure bladder but without the thick thermal/abrasion protection layers of the Extravehicular gloves they will wear outside the spacecraft. They are standing at the front of the spacecraft, looking out the windows and are held in place by tethers attached at the waist. In order to do the Descent Orbit Insertion (DOI) burn, they had oriented the spacecraft so that the engines would fire against their orbital motion around the moon and put them in a new orbit with a low point of 50,000 feet. Shortly after completing the burn, they put the spacecraft in the proper orientation for the powered descent. Because they were still about a half revolution from PDI, the new orientation meant that they were flying head forward, looking down at the Moon. Because the spacecraft would continue in the same orientation relative to the stars as it orbited the Moon, the orientation relative to the lunar surface would gradually change. As they came around the eastern limb of the Moon and got to a point a quarter orbit from PDI, they were flying with their feet pointed at the Moon and the windows pointed in their direction of motion. By the time they got to PDI, they were flying with their feet forward and their backs to the Moon.]

109:52:32 Conrad: Okay, what kind of azimuth with respect to the Sun will I have on that? Is it that little enough that I'm not going to notice it? (Long Pause)

[I asked if Pete's concern had anything to do with the location of the LM shadow during the final approach. The shadow can provide clues about their altitude, descent rate, and left/right rotation (yaw) relative to the flight path.]

[Conrad - "We were always going to have the Sun (more or less) behind us. I think I was wondering whether we were going to come in and be going across the crater from a direction much different from what we planned. We must have had some known Sun angle off our back if we were on the right ground track. And remember, a good part of our (site) recognition was shadow. So I wanted to know if five miles is a big change in the approach angle."]

[Bean - "That's right. He's not thinking about the LM's shadow during the final approach. He's thinking about the orientation of the landing site."]

[Conrad - "Yeah. We were going to approach it right up the Snowman, so it was going to be laid out in front of us. And I wanted to know if it was going to look different (because of any change in the approach trajectory caused by the fact that, at powered descent initiation (PDI), they were going to be 5 miles north of the nominal track)."]

[According to the Apollo 12 Mission Report, the crossrange error was eliminated during the powered descent so that, during the final approach, Pete and Al were flying virtually along the planned trajectory. Figure 4-4 in the Mission Report shows the lateral velocity imparted to the spacecraft to correct the trajectory. Note that the vertical axis on the plot appears to be mislabeled. 'Crew right' would be to the north and the desired velocity change was to crew left or south.]

109:52:58 Carr: Stand by, Pete. We're checking with the experts.

109:53:04 Conrad: Okay.

109:53:06 Bean (on-board): I'm not kidding.

109:53:07 Conrad (on-board): What?

109:53:08 Bean (on-board): The closer I get, the more I feel like it's just like landing on Earth. Just let it fly down and park it somewhere. We'll bound out and grab a rock. (Long Pause) Okay. (Pause) Let me read the PDI rules to you.

109:54:04 Bean (on-board): When I went to Voice Backup, it whistles. (Pause)

109:54:12 Bean: Houston; Intrepid. When I went (means 'put') my updata link to Voice Backup, it made a whistle on our Comm, so I'm just going to leave it off.

109:54:16 Carr: Roger, Al. (Long Pause)

[Bean, from the 1969 Technical Debrief - "I noticed, when we were coming into PDI, that there was a lot of background noise. I guess it must have been on the S-band. It had sort of a roaring, whistling sound, and it persisted for about 10 or 15 minutes. I don't exactly remember when it stopped, but it finally ceased so that, from PDI through landing, we didn't have that sound."]

[Conrad, from the 1969 Technical Debrief - "Yes, I remember that now. It didn't really interfere with the Comm(unications) because the voices were good and loud. This whistling, windy sound was on there."]

109:54:29 Conrad (on-board): Keep reading (the mission rules).

109:54:35 Bean (on-board): What can I do to help you, Pete? Let me cross them off for you.

109:54:46 Conrad (on-board): Okay.

109:54:48 Carr: Intrepid; Houston.

109:54:50 Bean: Go.

109:54:51 Carr: Roger. Now that you got a new RLS (Reference Landing Site), we've got a new address 231 for you.

109:54:58 Bean: Go.

109:54:59 Carr: Okay. 231 is plus 56957.

109:55:10 Bean: Plus 56957. Roger.

109:55:13 Carr: Roger.

109:55:14 Conrad: (To Gordon) Coming at you with the radar, Dick.

109:55:21 Gordon: Okay. (Pause)

[During the 1991 mission review, we had some confusion about this update. For a little while, Pete thought they still had one more orbit to complete before PDI and then Al thought that this update might have been an update to the PGNS, based on tracking data, that corrects the computer's target so that they would land close to the planned spot. Neither was correct.]

[Journal Contributor Frank O'Brien provides an explanation of the AGS 231 update - "At about PDI -30 minutes, the crew performs two critical activities with the guidance systems. First, Houston supplies a new State Vector and a revised location of the Reference Landing Site (RLS) by directly updating the LM computer. This update was begun at 109:50:52, when Pete entered P00 on the computer. Next, the AGS must be initialized with information provided from the PGNS. Part of AGS initialization requires manually entering the distance from the landing site to the center of the moon, measured in hundreds of feet. Here, Jerry Carr has informed the crew that the landing site is 5,695,700 feet (about 937 nautical miles) from the center of the moon. The AGS uses this value as part of it's orbital calculations."]

109:55:31 Carr: Intrepid; Houston. That whistle you heard, we think, was because we were still commanding. They'd like to have you try it again.

109:55:41 Bean: Just tried it; it looks good on the Voice Backup here.

109:58:01 Bean: Houston, our first perilune altitude check, using the tapemeter, shows that it's going to be about 57,500 (feet).

109:58:11 Carr: Roger, Al. Copy.

[During the 1991 mission review, none of us was certain that we understood how the perilune check was being done. As we discussed the question, Al read the following from the 1969 Technical Debrief.]

[Conrad, from the 1969 Technical Debrief - "Because we had very good agreement (between the PGNS and AGS on the velocity residuals after the DOI burn) we didn't exercise the rendezvous radar option and make a lock-on with the Command Module. We pressed on. Our computer showed that it (the burn) put us in a 60.5 by 8.9 (nautical mile orbit), which is very close to the Pads I used for DOI."]

[Bean, from the 1969 Technical Debrief - "The AGS showed 60.5 by 8.5."]

[Conrad, from the 1969 Technical Debrief - "We immediately went to the PDI attitude, which left us face down looking at the Moon. From that inertial attitude, we watched ourselves pass from face down through local horizontal (that is, facing forward with their feet toward the Moon), to pitch up (that is, face up, feet forward) at PDI. It gave us an excellent look at the Moon going around. We had a relatively easy checklist at that point. We reset the DAP (Digital Autopilot) and our twenty degree stick, and accomplished the checklist, put our helmets and gloves on, buttoned everything down..."]

[Conrad, from the 1991 Mission Review - "We reset the DAP for landing."]

[Journal Contributor Frank O'Brien explains the DAP update and the 'twenty degree stick': "The A12 LM Timeline manual currently available is missing the appropriate pages, but the A14 LM timeline page 4, right before the PDI algorithm check shows that the DAP settings: Verb 48, with register 1 = 22112. Translated that means:

Better translation: The digital autopilot was loaded with essential parameters that govern its control laws. The Ascent and Descent stages are attached, which define the mass distribution of the spacecraft. Translations in the +/-X direction will use all four jets, and only from RCS fuel system A. Manual maneuvers using the attitude controller are set to rotate the spacecraft at up to 20 degrees/second. Attitude will be held within a 1 degree deadband, and automatic maneuvers will be done at 2 degrees/second.

The '20 degree stick' is a reference to the third DAP value, which sets the manual maneuvering rate at 20 degrees/sec, much faster than the 'Fine' setting of 5 degrees/sec. It's reasonable that you would want this much control authority during PDI; if there was a problem with a runaway DPS gimbal or other controlability problems, you want to most aggressive maneuvering available."

Frank adds a caution: "There is one thing that bothers me about the documentation about the DAP setting. The details came from the A15 Delco manual, which is about as gospel as they get. Specifically, the second digit specified that '4 jet translation using Fuel System A'. Now, I interpreted that to mean +/- X translations, since those are the only ones that *can* be done using four thrusters. OK, that's fine. But, the specification of the fuel system is puzzling. By design, the RCS system has two independent fuel systems, and two of the +/- X thrusters use fuel system A, and two use B. The computer cannot command any crossfeed in the RCS system. So, I'm thinking that there is a typo in the A15 Delco manual; to do a 4 jet +/- X translation, you *have* to use both fuel systems. "]

[Bean, still quoting Pete from the 1969 Technical Debrief - "'Now we got to our perilune and altitude checks. And that's the place that we didn't realize any error could crop up.' That's where we are right now. 'It turns out that the predicted perilune and altitude checks at PDI are based on the Command Module being in some fixed orbit.'"]

[Conrad - (Not certain that the rendezvous radar could be used to track the CSM during this phase of the mission) "Yeah, but, remember what we said about the attitude. We went to an inertial attitude which was the PDI attitude. (Demonstrating the change in spacecraft attitude relative to the Moon caused solely by orbital motion) Here's the landing site, here's the lunar surface. PDI occurs when we're looking up, the engine's forward, the landing gear's forward."]

[During the approach to PDI on Apollo 11, Neil and Buzz rotated the LM around the thrust axis (that is, did a yaw maneuver) so that they would be looking down at the Moon during the first few minutes of the burn. This let them do some landmark tracking as a double check to the computer and the ground-based tracking to make sure they were on course. After completing the landmark checks, they then yawed back around to the face-up orientation. I asked if Pete and Al had done such a maneuver.]

[Conrad - "No. Neil and Buzz did, but we didn't. And the whole reason for that was that the antenna coverage was very shaky when they were face down. I remember they had a whole bunch of comm problems."]

109:58:16 Bean: (To Houston) Do you concur or not (with the 57,500 foot perilune)?

109:58:17 Gordon: Houston. Clipper.

109:58:19 Conrad (on-board): Got another one (meaning another altitude readout).

109:58:55 Carr: Roger, Al. (To Dick) Clipper, Houston. We think it probably won't do you much good to have it right now. It'd be better later.

109:59:05 Gordon: Okay. (Long Pause)

[Conrad, from the 1969 Technical Debrief - "It turns out that the predicted perilune and altitude checks at PDI were based on the Command Module being in some fixed orbit. It turns out that Dick was not in that orbit. We realized something was wrong with the checks because, not only did it show us high (compared with the expected perilune of 50,000 feet), but it didn't show a consistency. At each mark, our (indicated) altitude at PDI grew from 56,000 feet finally up to 64,000 feet, and the ground said 'Forget it,' because they had a good track on us and said we were still showing a 50,000-foot perilune - right on the money."]

[Bean, from the 1969 Technical Debrief - "I'd like to recommend that this check be eliminated. It's just busy work. As you can see, it didn't provide any intelligence that let us make a decision. No matter what the numbers would have come out on that, I think we would have gone ahead and made the landing just as we did, because it showed us diverging from our nominal PDI altitude and headed up (which was nonsense). So, unless we come up with something better - which I don't think we need with the way the PGNS is working and with good ground tracking - I think we ought to eliminate it. This will give you more time to prepare for PDI - to look out the window and (inside the cabin) make sure all is in order."]

[On later missions, several orbits prior to the time that the surface crew entered the LM and undocked from the Command Module, the CSM Service Propulsion engine was used to put the mated spacecraft into the Descent Orbit. This was done primarily to conserve LM fuel so that a heavier spacecraft could be landed, but it also gave Houston plenty of time to track the spacecraft and refine their knowledge of the orbit. Then, after undocking over the Farside, the CMP did a 'circularization' burn to put himself in a 60 mile circular orbit for rescue and/or rendezvous. Consequently, the requirements for PDI altitude determinations by the LM crew were much reduced and, although they did perform radar and VHF ranging checks prior to the descent, they did not use these as perilune checks and, instead, did only a few rough checks via landmark tracking.]

109:59:11 Bean (on-board): Clipper and Houston are clearing good.

109:59:14 Conrad (on-board): Man, this suit is too tight.

[See the discussions at 122:37:27 and 128:51:00 about the discomfort Pete is experiencing and his decision to wake Al up early prior to EVA-2 preps and have him re-lace the suit legs to give him a little extra length.]

[Most of this transmission refers to the fun Al's expecting they'll out on the lunar surface, wearing their bulky white suits and hopping around. The first part of the transmission, 'No, that's funny', doesn't seem to make sense in that context. Rather, Al may have been talking to himself about something he was seeing on the instruments or computer that didn't make sense to him and then responded to Pete's comment about his tight suit. Once we have a digitization of the on-board audio tape, we may be able sort this out.]

109:59:34 Conrad (on-board): Okay. Stand by.

109:59:35 Bean (on-board): Hang on there. Okay.

109:59:36 Carr: Intrepid, Houston. We're still looking at a perilune of 50,000.

110:02:49 Bean (on-board): I've read part of them. (Reading) "Delta-H within limits greater than 10 seconds and not out of limits greater than 60. Beta good at greater than 10 grand (meaning 'greater than 10 thousand')."

[The transcript published in December 1969 from the on-board recording has the following: "For flashing LANDING RADAR, ALTITUDE, or VELOCITY lights that are preceded by 30-cycle RADAR TEST
switch. Okay. That's it." Until we have a digital copy of the on-board recording, we will assume that Al simply read the PDI Abort Rules verbatim. It is possible that the '30' could be something Pete said.]

110:04:05 Conrad (on-board): It's not too bad right at the moment. (Long Pause)

110:04:33 Conrad: We look real good up here, Houston. How're you feeling down there?

110:04:37 Carr: Intrepid, Houston. We're feeling great. (Long Pause)

110:04:57 Carr: Intrepid, Houston.

110:05:01 Conrad: Go ahead.

110:05:03 Carr: Roger, Pete. On this Sun angle, or Sun azimuth, as far as we can see, there'll be no noticeable difference, as far as you're concerned. All you got to do is watch out and not fly through any clouds.

110:05:16 Conrad: Okay. I'll stay away from the clouds. And we're looking for the Snowman.

110:05:20 Carr: Roger.

[The Snowman is the cluster of craters that surrounds their target point. It can be seen slightly left of center on a large-scale map of the landing site. West is on the left. Surveyor Crater is centered at about N.3/29.5 and Head Crater - the Snowman's head - is immediately west of Surveyor Crater at N.4/28.6. The Snowman's feet are at N.4/30.7 and M.4/30.7. I have never been impressed that this pattern was easily called the Snowman. However, late in 1999, I was looking at one of the USGS site maps covering the immediate area around Surveyor Crater and really saw the Snowman for the first time. The key to success was to look at the map, LSE-7-6G with west at the top and to look, not at the craters, but at the white ejecta circles drawn around them by the geologists who prepared the map. As can readily be seen in a detail, the ejecta circles create a striking Snowman image. Although I can easily imagine Pete Conrad spotting the figure the first time he was shown the map, I do not yet know exactly how or when the Snowman got its name.]

110:06:48 Bean (on-board): I was just thinking about that while ago. We'll shoot right between a couple of them.

110:06:55 Conrad: I sure hope you have us lined up right, Houston, because there sure is some big mountains (laughing) right in front of us, right now. I hope we go down in the middle. There is one valley.

110:07:06 Carr: Roger, Pete. (Long Pause)

[They are about 14 minutes from PDI, or about 45 degrees east of the landing site and are probably crossing the highlands south of the Sea of Tranquility (see below). Also, because they are in an inertial attitude that will put them face up at PDI, their feet are now pointed about 40 degrees below horizontal.]

[Jones - "You could see those mountains out of the lower part of the window?"]

[Conrad - "There was a mountain range. I remember that. But the one where it really got me was Skylab. We'd been at 250 (nautical miles) and did a two-burn de-orbit. And we had a perigee of 90 (nautical) miles, coming up over the Andes. And, goddamn, we came smoking over the (Pacific) ocean and I saw those mountains out there and I said to Joe and Paul, 'God!'"]

[Pete commanded the first Skylab crew, and Al commanded the second.]

[Bean - "It did seem like we were just flying over in an airplane. Remember those big, white, salt lakes down in there?"]

The visual display that Carr is looking at in Houston is showing graphs of spacecraft performance rather than the flight path over the lunar surface.]

110:09:08 Bean (on-board): I don't want to look.

110:09:10 Conrad (on-board): (Laughter) There's nothing but rocks out there. (Pause) I hope we go a lot further on.

110:09:24 Bean (on-board): We do; we got a long ways to go. Got a - hundreds of miles after PDI, for Christ's sake. Already, we have 170 by 260 something ...

110:09:33 Conrad (on-board): 260, yes. (Long Pause)

110:09:50 Bean (on-board): 49, Pete.

110:09:52 Conrad (on-board): Okay. We've done this so many times, we'd better do it right. Don't let it get out of sight, don't get low, and don't try to fly too hard. I'd like to fly it there on LPD.

110:10:18 Bean (on-board): That's what I mean. This baby (meaning the LM Guidance Computer) can save gas for us. (Pause)

110:10:30 Conrad (on-board): I'll try to talk about as much as I do in the doggone simulator. If it looks like the gas is good, I'll say it; if it looks like we're too high or something, I'll say it, but I don't ...

110:10:36 Carr: Intrepid, Houston. You've probably just passed over Theophilus (which is a very large crater centered at about 27E and 11S).

110:10:43 Conrad: Okay. (Pause)

[The accompanying figure is a Lunar Orbiter photograph Dick Gordon would later use forlandmark tracking as he approached the proposed Descartes landing site where, on Apollo 16, John Young and Charlie Duke landed. Theophilus is at the lower left. Note that, in left part of the partial circle drawn around the Descartes site, the white ejecta blanket thrown out during the South Ray impact is easily visible.]

110:10:49 Conrad: Pretty darn rugged down there.

110:10:51 Carr: Roger. Tell us when you want us to turn on the mirror.

110:10:57 Conrad: You can turn the mirror on; give me the fox-corpen, and we got the hook down.

110:11:02 Carr: Roger.

110:11:06 Gordon: Roger. Fox-corpen, 285. Clear deck. (Long Pause)

[Conrad - "These are carrier terms. The mirror gives you the glide slope for landing on the carrier."]

[Gene Cernan provided the following explanation of the mirror during the Apollo 17 mission review.]

[Cernan - "When you land on a carrier, you've got a mirror and you've got an orange light that reflects in the mirror. On the carrier, you've got a row of green lights that also reflect in that mirror and if the meatball - the orange light - is below the green lights, then you are low, below the glide slope; and if the meatball's above the green lights, you are high. So what you do is fly your carrier approach so that the meatball is right in line with the green lights."]

[Conrad - "'Fox-corpen' is the recovery heading. It's like telling you what runway to land on."]

[Bean - "What direction the ship will be going. That way, you can brake and approach."]

[Conrad - "We were going to the west, so he's got us going 285 (15 degrees north of west)."]

[Jones - "And 'hook down' is, of course, the landing hook."]

110:11:44 Conrad: Interestingly enough, Houston, at this attitude, I still can see the lunar horizon. I have to really peer to find it, but I can see it.

110:11:56 Carr: Roger, Pete.

[They are about 9 minutes from PDI and their feet are pointing about 27 degrees below horizontal. Because of the shape and setting of the windows, it is not possible to look straight down along the thrust axis.]

[Conrad - "The window was triangular and you've got to..."]

[Bean - "(Finishing Pete's thought)...float up and look in. I kind of remember you doing that. Floating up and trying to look down in there."]

[Jones - "I gather that you didn't have the tie-down cords on at this point?"]

[Conrad - "Oh, yeah."]

[Bean - "I think we probably did and they were probably just loose. They were in the not-locked mode."]

["'5018' is Pete and Al's verbal shorthand for a computer request, 'Verb 50, Noun 18'. In this command, Pete is telling the computer to maneuver to the proper attitude for PDI. Although they have been flying essentially in this attitude, this command will correct for any drifting that may have occurred. On the DSKY computer display, the Verb and Noun codes are displayed side-by-side, which lead the crews to adopt the convention of reading the display as a single number."]

["Use of this shorthand is an excellent example of how well the crews worked together. Both crew members had rehearsed this phase of the mission countless times, and communication between the two was actually enhanced by eliminating 'unnecessary' phrases. This shorthand surfaces again at 110:22:18, when they make a correction in their landing site targeting."]

[They are switching to voice-activated comm. Prior to this time, they were in the Push-to-Talk (PTT) mode where, if they wanted to talk to Houston, they had to squeeze a trigger switch on the hand controller in order to transmit. In PTT, anything they said was carried on the LM intercom so that, even with their helmets on, they could talk to each other without having to use the switch.]

110:19:30 Conrad: On my mark, it will be 1 minute (to Powered Descent Initiation, the start of the engine burn that will take them down to the surface).

110:19:39 Conrad: Mark. One minute.

110:19:41 Bean: Watch is started, Pete.

110:19:44 Carr: (Acknowledging Pete's mark) Roger, Pete.

[Al has started the LM Digital Event Timer (DET).]

[Bean - "Didn't we have it set at minus one minute or something like that? That we didn't have to start it on time."]

[Conrad - "Right. Everything had a certain time phase and I'm sure you were starting the clock. Or you started your own (wrist)watch."]

[Bean - "No, I started my watch whenever the fuel light came on. I wonder why I didn't say 'clock is started.'"]

[Conrad - "I don't know."]

[Bean - "It seems to me we put the event timer on minus one. And, then as it went through zero, it just kept going and counted up like everything else."]

[In a 2004 paper, Tales from the Lunar Module Guidance Computer, Don Eyles wrote, "At 35 seconds (before ignition) the display went blank, and at 30 seconds reappeared. This was a signal that Average-G (which integrated acceleration over a two-second interval for a smoother guidance solution) had started."]

110:20:16 Bean: (Garbled) nice. Steady couple of lights, there.

110:20:18 Carr: Copy, it's Armed.

110:20:19 Conrad: And an altitude light. (Pause)

[Jones - "The way I understand it, the velocity light means that the radar has not yet got a signal. That the computer is ready to take velocity data from the radar but doesn't have any. Is that right? Because, when you get a radar lock, the velocity light goes out."]

[The fuel and oxidizer tanks also contain pressurized helium. In zero-g, there is no way of telling where the helium is in the tanks and, just prior to ignition, the computer - with Pete doing a manual backup - will apply a small amount of thrust with the RCS jets against the orbital motion. This small acceleration will move the low density helium away from the exit valves that take the fuel or oxidizer to the Descent engine. The word 'ullage' denotes the portion of a cask that is empty.]

[Jones - "From Gene, my understanding of ullage is that you're making sure that the helium isn't near the feed into the engine, that you've got propellant going in there rather than helium."]

[Conrad - "Yes. But it's also the oxidizer, too. So you start the little thrusters burning, which gives you some g in the right direction so that, when the engine lights, you've got all the propellant at the bottom of the tank."]

110:20:47 Bean: Okay. Throttle up at 26 (seconds into the burn; that is, at 110:21:06).

110:20:48 Conrad: Yup.

110:20:49 Carr: Copy, throttle on.

110:20:50 Conrad: (To Al) I can hardly hear you for some reason. (Responding to Carr) Okay. Standing by for throttle up, Houston.

110:20:58 Bean: Pete, it looks good. (Pause)

[For the first 26 seconds of the burn, they have been running at 10 percent of maximum thrust in order to let the computer monitor performance. At the same time, the descent engine gimbals have moved the thrust vector so that it passes through the LM's center of mass. They are now increasing thrust to 93 percent of maximum.]

[The RCS consists of clusters of thrusters, each containing thrusters oriented along the three-principle axes of the spacecraft. They can be fired in various combination to give rotation around any axis or translation along any axis. In order to get proper pointing of the descent engine, the computer is making brief RCS firings every once in a while.]

[Conrad, from the 1969 Technical Debrief - "We had ignition on time and the engine was very smooth. It throttled up on time. We started down the trajectory and, because I could not see the ground, I religiously kept my head in the cockpit and used the Enter button at 30 seconds, 1 minute, 1 minute and 30 seconds, and right on down the line, carefully checking the PGNS first as to predicted values, while Al checked the AGS versus the PGNS. The AGS and PGNS stayed in very, very good agreement."]

[During the mission review with Pete and Al, I noted that, by the time of Apollo 17, Jack Schmitt and the computer experts in Houston had been playing with the AGS enough that they thought they could probably land with it. I asked what the status of the AGS was at the time of Apollo 12.]

[Conrad - "It was not designed to do that. Ours was strictly abort."]

[Bean - "If you ever aborted, then the AGS was the backup so that, if your PGNS went down, then this would actually guide you. Otherwise (in a normal descent or ascent), it was just a backup (to the PGNS)."]

[Conrad - "Yeah, but if the PGNS went down, you were going to abort. You were not going to go ahead and try to land."]

[Conrad - "Yeah. And that's plus 4200 feet. We had very low errors. And there should be another one in there for crossrange in there someplace. No, I guess not. Well, we could make a crossrange correction but I guess we didn't have to. We must have been right on our azimuth."]

[Journal Contributor Paul Fjeld notes that the ability to update the LM targeting "was added on Apollo 12. DLAND - Noun 69 - was a dangerous vector! It was added to the Position of the landing site (RLS) every 2-second cycle, then zeroed. The crew had to verify that the three registers were all balls (all zero), then only put the Delta Z value (downrange change in position) in R1, then only press enter when MCC looked at the DSKY downlist to verify that the number was good. Noun 69 was one of the easiest opportunities for the crew to kill themselves."]

[Bean - "2169 means load only the first register in 69. So it's the only one that blinks. Is that right?"]

[Conrad - (Laughing) "You're a lot further ahead than I am."]

[Bean - "No. I think that's right. It keeps you from having to fool with the others when they're already correct. That's why we're discussing it. Since we only have one number to put in."]

[The following was provided by Journal Contributor Frank O'Brien]

[Al is referring to the computer command Verb 21, Noun 69. Noun 69 is the targeting correction display and the three registers on the DSKY correspond to downrange, crossrange and altitude corrections. Verb 21 changes only the first register, which in this case is the downrange targeting correction. The sequence used to enter this command is to press Verb, 21, Enter, Noun, 69, Enter. The first register begins blinking, indicating it is ready for input. Al then keys +04200 Enter (all decimal values must be entered with their sign). After the Enter key is pressed, the display stops blinking.]

110:22:23 Carr: Intrepid, Houston. Go for enter.

110:22:29 Bean: It's in, babe.

[Conrad, from the 1969 Technical Debrief - "We entered it. The ground read it so that it was okay (that is, Houston monitored the entry to confirm that they had keyed in the right number). We pushed it into the computer (that is, by pushing the Enter button, they told the computer to use the update). This seemed to be the right number, later on, because it looked like we were targeted right dead smack in the center of the (Surveyor) Crater."]

110:22:34 Carr: Intrepid, Houston. Looking good at 2 (minutes into the burn).

110:22:39 Bean: Okey-doke.

110:22:40 Conrad: Roger.

110:22:41 Bean: PGNS and AGS are hanging in (that is, agreeing with each other). (Pause) Looks good here.

110:22:51 Carr: Roger. MSFN agrees with PGNS and AGS.

[The Manned Spaceflight Network is the array of stations on Earth which provide communications and tracking. Houston is telling them that the computers on Earth agree with the on-board navigation computers.]

[The Explosive Device batteries supply electric power to the explosive charges with which, in an emergency, the astronauts can separate the ascent stage from the descent stage and return to orbit.]

[Bean - "What happened was...First of all, it was the very last sim before the flight."]

[Conrad - (Laughing) "Yeah, I remember. We were all suited..."]

[Bean - "And it seems to me...I don't know what switch, (but) I threw the wrong switch. But, see, mission control didn't know it (because) they (the simulation team) had protected us out there at the simulator station so that the sim wouldn't go down. So I threw the battery switch - and I don't remember which one. It was a big mistake, a big disaster. But they protected us and nobody at mission control knew, so I just put them back on and they all came on. Even our computer wasn't down. And that's why Pete's laughing, because it was the very last day. I don't remember what we did. I did something dumb."]

110:23:38 Conrad: There they go. Three minutes. About 44 feet per second fast. About 6 feet per second low on H-dot. And about 100 feet low on altitude. Looking good.

[H-dot is the time derivative of altitude and, therefore, the rate of descent. The computer is fine-tuning their descent path to get them to the updated target, which now is farther west by 4200 feet.]

110:23:58 Conrad: Okay, Houston. (Pause; With pleasure in his voice) I have an altitude light out and a velocity light out.

110:24:07 Carr: Roger.

[Frank O'Brien - "When the altitude and velocity lights go out, it indicates that the landing radar is getting good data. At this point, the computer is not using the data, and will not until Pete directs the computer to do so at 110:24:26."]

110:24:26 Conrad: No sooner said than done. Let me know when it converges. I'm going back to my normal displays.

110:24:35 Carr: Okay, Pete. (Pause)

[They are now getting returns from the landing radar. Delta-H is the difference between their actual height above the surface and their altitude relative to the landing point. As they fly over mountains, the radar altitude will decrease and give a negative Delta-H. They have a chart giving Delta-H as a function of time into the burn and know what the reading should be. Agreement between the chart and the computer readout gives them confidence in the radar data.]

[Jones - "The way I interpret minus 918, minus 1000 is that it's the difference between the flight plan and the radar."]

[Conrad - (Reading from the tech debrief) "Our Delta-H, the first time I noticed it, was 1100 feet. And it had some noise on the radar. It jumped to 1900 feet and steadied out between 1100 and 1900. We watched it for a few seconds, and the ground gave us a good update which we did. I'm sure we were taking radar data at some 39,000 feet."]

[The last word in Al's transmission was originally transcribed as 'spacecraft' in both the Technical Air-to-Ground and LM Onboard Voice. However, Pete's comments below only make sense if Al is referring to him and Pete in the suits. Sometimes I think I hear "spacesuits", but that may be wishful thinking. If Al did say 'spacecraft', I believe he meant 'spacesuits'.]

[Conrad - (Laughing heartily, even 25 years later) "Remember, that fucking gauge never moved. We were convinced that there was never anything in there, other than the gauge. There was no sensor or something."]

[Jones - "And the two winners are the two bozos flying the spacecraft?"]

[Conrad - (Laughing) "Maybe so. We never ever - no matter what happened - we never had any CO2 and, of course, we're in the suit loop."]

[Pete and Al are hooked up to the ECS Suit Loop and are getting oxygen through hoses connected into the suits. They are, of course, exhaling carbon dioxide, but the lithium hydroxide canisters are doing such a good job removing the CO2 that the sensor is unaware that anyone is in the spacecraft. Consequently, 'two winners' is a bit of self-deprecation meaning that they can't even get a sensor to take them seriously.]

110:25:22 Conrad: Okay. We're out of 35,000 (feet).

110:25:25 Carr: Roger, Pete.

110:25:26 Bean: (We) maneuvered a bit on that one.

[The computer is responding to the radar information and is firing the RCS thrusters more often than it had been.]

[Conrad, from the 1969 Technical Debrief - "The other comment I have in P63 - and it didn't bother me too much, although I commented to Al about it several times - was the fact that we had considerably more RCS activity than we had noted in the simulator. But Neil also mentioned that, all the way down, he had more RCS activity than he had noted (in the simulators). So, I think this is due to radar updating."]

[Conrad - "The RCS started banging around. Remember, the engine was supposed to figure out how to trim itself."]

[Bean - "That's right. It was supposed to trim out the center-of-gravity errors by watching the RCS"]

[By gauging the response of the LM to RCS firings, the computer can correct for any displacement of the actual center-of-gravity from the nominal center.]

[Conrad - "Right in here, I started wondering whether it's trimming or not. And in the simulator we never ever saw it (have so much RCS activity). It would always figure everything out - boop, boop, boop - and that was it. In this thing (the actual LM), it banged all the way down."]

[Pete's colorful 'boop, boop, boop' - accompanied by a hand gesture indicating somebody quickly checking off items on a list - was meant to indicate that the LM simulator wasn't hesitant, that it did not have to correct itself with RCS firings, and that it always seemed to fly a smooth descent.]

110:25:27 Conrad: Yeah, I'm getting a fair amount of RCS firing. More than I think I should. But how does the gimbal look to you guys, Houston?

110:25:34 Carr: They're looking good, Pete.

110:25:38 Conrad: Okay. There's a five minute hack, Al.

110:25:43 Bean: Okay.

110:25:44 Conrad: Boy, it's really giving her heck on the RCS. That must be the radar updating.

[With the radar data now available, Al has a chance to correct the AGS. The AGS uses strap-down gyros to calculate three-component spacecraft velocities and is inherently less accurate than the inertial PGNS system.]

110:25:56 Conrad: It (the RCS) really is banging it (the LM) around, isn't it? (Pause)

[Conrad, from the 1969 Technical Debrief - "The throttle down did not happen quite as predicted. It seems to me we were off by a second. I think they gave us a throttle down at 6 plus 22, and we throttled down at 6 plus 23 or 24 or something like that. But it was close enough that we felt that that part of it was going right."]

[Conrad, from the 1969 Technical Debrief - "Every once in a while, I took a peek to see if I could see the horizon; and, along around 25,000 feet, I could see the horizon out of the bottom of the window, but seeing it didn't help, so I went back to the gauges."]

110:27:40 Carr: Intrepid, Houston. Monitor descent fuel 2.

[There are two fuel gauges and Houston believes either that number 2 is giving the best reading or the most conservative reading. The consensus among the astronauts is that it was the most conservative reading - the lowest believable reading.]

[Bean - "Yeah. Provided they thought it was working. If they thought they had a failure, they'd pick the other one."]

[Conrad - "See, even if it read higher than the other one, if they thought it was the most accurate, that could mean that the other one - even though it's more conservative - the error could be in the wrong direction. So, I think it's really both. If you pick the most accurate, you are picking the most conservative. Although somebody might argue with that."]

[Bean - "I guess that, in decision making, we needed the one that gave us the most accurate understanding of what's going on. So I think maybe Pete's right. You want to know with the best accuracy anybody can come up with, which is right. And they're telling us. Use that one and that'll give you the best."]

[Bean - (Laughing) "But I would never use the expression 'Let's smoke over the gauges.' If anybody says that, it's Pete. But I also think that, after you've worked together for a long time, you do start to sound alike."]

[Journal Contributor Tomas Lundberg notes that Al is wrong about never using the expression 'Let's smoke over the gauges'. He does so at 110:33:09.]

[Their horizontal velocity is now 1153 fps and their descent rate is 135 fps. Both differ only slightly from the planned values and, then, only because of the target update caused by the differences in their actual orbit at PDI and the planned orbit.]

110:28:21 Conrad: (Garbled).

110:28:22 Bean: Everything looks good.

110:28:24 Conrad: 160 feet a second, huh?

110:28:27 Bean: Okay. 23. We'll be there in a minute.

110:28:28 Conrad: In a minute. Number.

[Al's next transmission - and tone of voice - suggest that Pete has just said "camera" instead of "number".]

[Conrad - "With (aircraft) ejection seats, when you pass 10,000 feet in the airplane, you always hooked up what's called the low-altitude lanyard. When you eject above 10,000 feet, you don't want the 'chute to open until you get to 10,000 feet."]

[Bean - "The lanyard was hooked to the seat so that, when you got free of the seat it pulled your chute."]

[Conrad - "You didn't want that to happen above 10,000 feet, so you didn't have the lanyard on."]

[At about 108:55:28, about a half hour before to Descent Orbit Insertion, Pete checked the accuracy of the sighting device he will use for the final approach. The Landing Point Designator, or LPD, consists of scribed vertical and horizontal scales on both panes of the window in front of him. Once Pete has positioned himself so that the inner and outer scales are aligned, Al can read a number from the computer which tells Pete where to look on the vertical scale to find the place where the computer thinks they are going to land. He can then use the handcontroller to move the target. Prior to pitchover, he did a sighting on a star and found that it was right where it was supposed to be.]

[Journal Contributor Ulli Lotzmann has provided a still frame ( 161k ) showing the LPD scales during a LM-inspection TV broadcast done during the trip out from Earth. Ulli captured the frame from material provided by Mark Gray.]

[Randy Attwood has provide a photo of the LPD scale in LM-9, the H-mission-capable vehicle scheduled for Apollo 15 before that flight became a J-mission.]

[P64 is the computer program to be used at pitchover. Once Pete tells the computer to proceed with the program, pitchover will begin.]

[The following was provided by Journal Contributor Frank O'Brien.]

[There were three major programs that were used during the descent. P63 performed the initial braking maneuver. During the first several minutes of the descent, P63 slowed the LM down and put it in a position east of the landing site and several thousand feet above the surface, with low horizontal and vertical velocity. At this point, the computer automatically called up P64 for the approach (or visibility) phase about 2-1/2 to 3 minutes before touchdown. When P64 is started, the LM is pitched over, and Pete has his first good look at the landing site. The LPD display is then called up by pressing the PRO[ceed] key on the computer. This phase of the descent was designed to give the Commander a good look at the landing site, and the computer continuously updated its estimate of where the LM was headed through the Landing Point Designator. The LPD is used only during P64, which ends at several hundred feet above the surface. Pete and Al's discussion of the 'LPD time remaining' at 110:29:58 refers to the computers display, which contained the LPD angle, the LPD time remaining, plus computed altitude and altitude rates. At the end of P64 (occurring when LPD time is zero) or by manual request, the P66 manual landing program is started. The crew uses this program until touchdown. Guidance and targeting information at this point is of little value, as the crew has already selected a general landing spot, and is now preoccupied with avoiding obstacles.]

110:29:03 Conrad: I'm trying to cheat and look out there. I think I see my crater.

110:29:08 Bean: (Garbled)

110:29:09 Conrad: I'm not sure.

[Pete is leaning forward, pressing his helmet against the window in an attempt to see the landing site. Figure 4-9 from the Mission Report shows a portion of a view Pete might have had in the LM simulator. Head Crater is the large crater just below the top of the image. Surveyor Crater, which is 'his crater', is the larger crater below Head Crater. The bottom left image shows the view at pitchover as seen by the 16-mm camera mounted in Al's window. The sketch at bottom right includes an outline of the Snowman. In Pete's view, the Snowman is to the right of center. Note that, in the two bottom figures, the large crater beyond and to the right of the Snowman is Middle Crescent Crater, which Pete and Al will visit at the end of EVA-1. The craters are labelled in a better version of the view from the simulator window. ]

[In the Landing Point Designator mode of operation, Pete can use his handcontroller to re-target the LM. If he wants to redesignate the target, he clicks the handcontroller left or right, forward or back to get a small change; or he gives several clicks to get a big change.]

[Conrad, from the 1969 Technical Debrief - "As soon as we got to the pitchover maneuver, I proceeded on the computer to enable LPD (P64) and immediately went outside the window."]

110:29:17 Carr: Roger. Copy P64.

110:29:18 Bean: Okay, there's 6000 update.

110:29:20 Conrad: (Very excited) Hey, there it is! There it is! Son-of-a-Gun! Right down the middle of the road!!!

[It's taken a few seconds for Pete to recognize the Snowman.]

[Conrad, from the 1969 Technical Debrief - "For the first couple of seconds, I had no recognition of where we were, although the visibility was excellent. It was almost like a black-and-white painting. The shadows were extremely black, illustrating the craters; and, all of a sudden, when I oriented myself down about the 40-degree line in the LPD, our five-crater chain and the Snowman stood out like a sore thumb."]

[Conrad - "What's really funny is that I've got some other conversation in my mind that I didn't hear. Because I (have) thought I couldn't find it."]

[Bean - "That's what I thought."]

[Conrad - "(What I remember is that) you gave me the number and then I found it!"]

[Bean - "I gave you the number and you looked through the window..."]

[Conrad - "The number is the down angle..."]

[Bean - "That's what I remember. That's what I've told people."]

[Conrad - "That's what I remember."]

[Bean - "Isn't that funny."]

[We listened to it again and, then, Pete realized that what probably happened is that, when he enabled P64, he saw the angle on the display and that told him where to look.]

[Bean - "That's the part of the program when those numbers come up."]

[Conrad - "Yeah. So I think I'm reading (the number, rather than getting it from Al). When I say this ('there's LPD') I'm reading the number."]

[Bean - "That's right. I'm not saying it, but you've read it."]

[Conrad - "Yeah. I know I didn't know where the fuck I was! I looked out and I didn't know where the hell I was. I looked (at the computer) and got the number. I looked back through the number and then I knew where I was."]

[Conrad - "Yeah, I know. But I'm up here like this (up on his toes, leaning forward) and I can see some craters out there, but what I saw was not (a pattern he recognized)."]

110:29:25 Bean: Outstanding! 42 degrees, Pete.

110:29:27 Conrad: Hey, it's targeted right...

110:29:28 Bean: 42.

110:29:28 Conrad: ...for the center of the crater!

[Figure 4-2 in the Mission Report indicates that they are about 4800 ft above the landing site and figure 4-8a indicates that they are about 18,000 ft uprange. The crater would appear as a thin elipse about two degrees wide. Figure 1-9 from the LM Operations Handbook shows the LPD grid from inside the cabin.]

110:29:29 Bean: (Garbled) look out there.

110:29:30 Conrad: I can't believe it!

110:29:32 Bean: Amazing!! Fantastic! 42 degrees, babe.

110:29:35 Conrad: Just keep talking (garbled under Al).

[Although it is difficult to tell the two voices apart in this sequence, I am certain that I have the sequence correct. A plausible interpretation of this exchange is that, for just a moment, Al looks up from the computer to look out the window, and then goes back to his work. In an October 13, 1994 telephone conversation, Al said that, while he had no clear memory of looking out the window, it is likely that he did. The LPD number was not changing, Pete was not maneuvering, and there was no doubt that, if he did look up, he would see the Snowman. He said that it was very likely that he did glance up.]

[Conrad, from the 1969 Technical Debrief - "I started asking Al right away for LPD angles. As best I could tell, we had absolutely zero out-of-plane error. We were targeted right dead smack in the middle of the Surveyor crater and I just left it alone. I didn't LPD for quite a while, until we got down around, as I remember, 2300 feet or so."]

[Journal Contributor Paul Fjeld - "Up on the CDR's main panel beside the timers were two small digital EL (Electro-Luminescent) displays that showed fuel and oxidizer percent remaining. The crew could monitor either set of tanks by pushing the PRPLNT QTY MON switch to DES 1 or DES 2 depending on which was more conservative (Houston would make the call). The LMP would just look over and call out the lowest number."]

110:29:45 Carr: Intrepid, Houston. Go for landing.

[Between now and about 110:30:42, Pete will make seven target redesignations before switching to manual control (P66) at 110:30:50. He will only mention two of these in transmissions from the LM and mentions one other - albeit out of sequence - during the Technical Debriefing. Details of the redesignations can be found in Table 4-I and figures 4-11a and 4-11b from the Mission Report.]

110:29:47 Conrad: Okay; I'm going to click over one. I just want LPD to the right (north) a little.

[Table 4-I gives the time of this first redesignation as 110:29:44. They are at about 2600 ft altitude and 12,000 ft uprange. The cross-range angular diameter of Surveyor Crater is about 2.8 degrees and they are looking down on it on and angle 12 degree below horizontal. Along the the direction of flight, the apparent height of the thin elipse is about 0.6 degrees.]

110:29:50 Bean: (Responding to Carr) Roger.

110:29:51 Conrad: Okay. Roger.

[Conrad, from the 1969 Technical Debrief - "I LPD'd one right to move it off the crater, and headed to the landing area short of the crater."]

[During mission planning, they had picked provisional landing spots at four places around the crater and planned geology traverse starting from each of them.]

110:29:52 Bean: 40 degrees, LPD, Pete; 40 degrees.

110:29:53 Conrad: That's so fantastic, I can't believe it!

110:29:55 Bean: You're at 2000 feet.

110:29:57 Conrad: How far?

[Conrad, from the 1969 Technical Debrief - "At that point, I listened to some more LPD angles from Al and I had a feeling that I was a little high; so I LPD'd two clicks short, and I let it go for a while."]

[Table 4-I indicates that Pete actually did these "two clicks short" later in the sequence of redesignations - at about 110:30:30 - and, therefore, that he was mis-remembering the order in which he did the sequence of redesignations.]

[Pete's preferred landing site is just northeast of the crater, a spot that came to be know during training as "Pete's Parking Lot". However, according the Journal Contributor Paul Fjeld, propellant slosh is making the LPD readings unreliable. The computer isn't taking Pete where he thinks it is. See a discussion after 110:31:05.]

110:29:58 Bean: The boys on the ground (meaning the trajectory experts who have them right on target) do okay. 1800 feet up, 39 degrees; you got 94 seconds of LPD time left.

[Conrad, from the 1969 Technical Debrief - "Then I decided that I was going to land a little short and Al called out something like '30 seconds of LPD remaining'."]

[Bean, from the 1991 mission review - "LPD remaining?"]

[Conrad - "Well, we must have had some limits. In other words, you could LPD yourself out of fuel. And out of the envelope that would run you out of fuel."]

[Bean - "Somehow I was reading that time. As I remember it, it was only (between) certain altitudes you could LPD. Because, when you got close, then if you tried to LPD it would cost you more fuel than if you just flew it over there (manually). So maybe what I was doing was looking on my little chart; you know, the one that says 10,000 feet or something. It probably had on there 'At 12 minutes you can't LPD any more' or something like that."]

[Conrad - "I have no memory of any of this stuff (in the debrief)."]

[Readers who missed it may want to consult the discussion at 110:29:02 which clears up this point.]

[Conrad, from the 1969 Technical Debrief - "I gave her one click forward, let her go for a while, and decided that we were high and fast. I didn't like the size of the area short, where we had normally been trying to land, and I looked for a more suitable place. ('That much I remember,' Pete said in 1991.)"]

[Pete actually did two clicks forward. One at 110:30:02 and the other at 110:30:06. At the time of the second click forward, Figures 4-2 and 4-8a show they were at an altitude of about 1300 ft and uprange about 7300 ft. The crater's angular diameter is now 4.6 degrees; and it's apparent height, 0.4 degrees]

[During Al's long transmission, Pete does a redesignation to the right (north) at 110:30:12. Then, at 110:30:30, Pete does the "two clicks short". Their altitude is about 600 ft and, as can be seen in figure 4-8a, they are about 4000 ft uprange. The crater's angular diameter is about 8.5 degrees and it's height 1.1 degrees.]

[At 110:30:42, Pete does one last redesignation - one click to the right - before switching to manual control.]

110:30:47 Conrad: I got it.

110:30:48 Bean: 400. You're in P66, Pete.

110:30:51 Conrad: Right.

110:30:52 Bean: P66. Okay.

[Pete is now out of the LPD mode and will now use the hand controller to fly the LM manually.]

[Conrad, from the 1969 Technical Debrief - "At the same time, I took over manually at about 700 feet and immediately killed the rate of descent. It looked like we were going to ground like a bullet. I had plenty of gas and I wanted enough time to look around."]

[We briefly returned to the question of 'LPD time left'.]

[Bean - "I think there was only a certain period you could do it (meaning that LPD could only be used while in P64).]

[What Al is trying to remember - nearly 22 years after the mission - is that LPD was available while they were in P64, which would last until they reached 'low gate' at an altitude of about 500 feet and a range of about 2000 feet. If Pete hadn't switched to manual control (P66) by that time, the computer would have switched to P65 and LPD would no longer have been usable. See a discussion of the Apollo On-Board Computers by Phill Parker.]

[Bean - "And I must have had my stopwatch on it. And just reading and saying, 'Hey, you can only do this 30 more seconds.' And, when you get pretty low, like you said, then you took over manually. I can't remember how you made it quit being LPD and starting making it just manually flying."]

[Conrad - "That was just a program change (to P65 or P66)."]

[Jones - "P66."]

[Bean - "Oh, that's it. When you want to fly it, you had to get out of that program."]

[Conrad - "I guess P66 was manual only."]

[Jones - "I think so."]

[Journal Contributor Frank O'Brien confirms that P66 is used for the manual control portion of the landing. See a discussion of the Apollo On-Board Computers by Phill Parker. LPD was available while in P64, which would last until Pete took manual control or until the computer automatically switched to P65 when they got to 'low gate' at an altitude of 500 feet and a range of 2000 ft.]

110:30:55 Conrad: Yeah. I got to get over to my right (north).

[By this time, Pete realizes that, if he is to land on the north side of the crater, he needs to be farther to his right. There is clearly a difference between where the computer was taking the LM during the time the LPD was active and where Pete thought it was taking him. Two possibilities come to mind. First, that Pete wasn't properly aligned with the LPD grid; and, second, that the numbers Al was getting from the computer didn't correspond to the actual target.]

[Fjeld - "We all know what happened on Apollo 11. Slosh uncovered the Quantity Gauge, latching the (Quantity) light early, losing the crew half a minute of flight time. It also made the LPD unreliable. Apollo 12 flew with the same configuration and its Quantity light came on early, exactly the same way! Worse, Pete actually used the LPD to redesignate his landing, but he maneuvered away from his target because the slosh was messing up his view through the grid. He popped out of P64 and tried to slam on the brakes but it was too late ("Gosh! I went by it!"), so he had to make his heroic flight around the crater, scaring Al a bit. He would have been better off never using the LPD, letting the flight path settle out, switching to manual just before the crater, and landing uprange and north of the crater!"]

[Pete's maximum northward position comes about 75 seconds prior to the landing, or about 110:31:21. According to figure 4-11a in the Mission Report, he is about 300 feet east and about 150 feet north of the eventual landing spot.]

110:31:21 Bean: Come on down, Pete.

110:31:22 Conrad: Okay.

[Pete is descending very slowly as he flies along the north rim of Surveyor Crater, looking for a good spot to land.]

[Conrad, from the 1969 Technical Debrief - "At that point, Al got a little nervous because I had killed the rate of descent to 3 feet a second at 500 feet. I left a very high pitch angle on it, on the order of 30 degrees, because we were moving quite fast and I wanted to get stopped."]

[Pete has the spacecraft pitched so that the engine is pointed partly forward to slow their approach to the landing site.]

[Conrad, from the 1969 Technical Debrief - "I had the horizontal velocity under control about the time I passed the near (eastern) edge of the Surveyor crater (at about 110:31:00). I saw a suitable landing area between the Surveyor crater and Head Crater, which meant I had to maneuver to my left and sort of fly around the side of the crater, which I started to do. I guess I wheeled her around it pretty hard, because Al commented a couple of times that I was really cranking her around; and I told him it was no problem."]

[Conrad, from the 1969 Technical Debrief - "I had everything under control, and I did increase the rate of descent after he called my attention to that fact that we had leveled off quite high, at 500 feet (actually about 200). I got down as soon as I got over the area that I wanted to land on. To me, it looked like a perfectly smooth, good area, between Head Crater and Surveyor Crater, and I started a vertical descent from a relatively high altitude, 300 feet at least. It may turn out that I actually backed up a little bit (that is, move backwards during the descent); but I don't think so." (He didn't.)]

[Because Al is concentrating on the computer, Pete may already be seeing dust.]

[Conrad, from the 1969 Technical Debrief - "As soon as I got the vehicle stopped in horizontal velocity at 300 feet (figure 4-12 (redrafted by Thomas Schwagmeier) from the Apollo 12 Mission Report indicates that he stopped almost all of his forward motion at about 220 feet), we picked up a tremendous amount of dust - much more than I had expected. It looked a lot worse than it did in the movies I saw of Neil's landing. It seemed to me that we got the dust much higher than Neil indicated. It could be because we were in a hover, higher up, coming down. I don't know. But we had dust from - I think I called it around 300 feet. I could see the boulders through the dust, but the dust went as far as I could see in any direction and completely obliterated craters and anything else. All I knew was (that) there was ground underneath that dust. I had no problem with the dust, determining horizontal (fore and aft) and lateral (left and right) velocities, but I couldn't tell what was underneath me. I knew I was in a generally good area and I was just going to have to bite the bullet and land, because I couldn't tell whether there was a crater down there or not."]

[Pete does not want to land with one or two legs in a crater large enough to give the spacecraft a significant tilt. Visibility of rocks and small craters looks better in the Apollo 12 DAC film than in the Apollo 11 film and Pete may be referring to craters big enough to bother the LM.]

[Conrad, from the 1969 Technical Debrief - "We came down at a relatively low descent rate. I think I speeded up to about 6 ft/sec and got her down around 100 feet, where Al called it (that is, told Pete to slow the descent), and I slowed to about 3 ft/sec and started milking her down."]

110:32:07 Bean: 46 (feet).

110:32:09 Carr: Low level (fuel warning).

[Carr is alerting Pete and Al to the fact that their propellant quantities are now down to 5.6 percent. In the LM cabin, the Propellant Quantity Light has come on to convey the same warning; but Al has not called out the light.]

[Journal Contributor Mike Harney calls attention to a 25 November 1968 memo from Howard Tindall concerning the low-level warning. This is one of a series of Tindall memos fondly called 'Tindallgrams' by the recepients.]

[Journal Contributor Paul Fjeld further notes, "The Quantity Light and the Low-Level light are the same thing. It is up on the CDR's main panel warning lights as 'DES QTY' (see the grouping of ten annunciator lights just under the title word 'LUNAR' at the top of the accompanying diagram) and it comes on when the lowest propellant tank indicates 5.6% remaining - good for about 114 seconds of flying time at hover (meaning 'level flight') at about 25 percent throttle."]

["The master-alarm is the big, red, square button in front of each astronaut that lights up and is accompanied by a 3KHz tone (bells and whistles) that requires the astronaut to push it to reset. I guess Grumman jumpered the wires to keep the QTY light but removed it from the Master Alarm because there never was an alarm when the QTY light went on."]

["Ironically, without the tone, the LMP had to notice the QTY light to start his stopwatch count to one minute 34 seconds, which was 'BINGO fuel' or 'land in twenty seconds or abort now'. I'm sure every LMP was late in noticing the QTY light, but fortunately the ground got the Low Level Signal and was prepared to make the BINGO call."]

[Journal Contributor Frank O'Brien adds, "I'm sure that the 'wires were cut', as recommended in the memo, soon afterwards. Given the date (Nov '68), the relative ease of the fix, and the imperative to make Pete Conrad a happy man, I wouldn't be surprised if this was taken care of before Apollo 9, for which Pete was the Backup Commander."]

[Conrad, from the 1969 Technical Debrief - "At that point, the dust was bad enough and I could obtain absolutely no attitude reference by looking at the horizon and the LM. I had to use the 8-ball. I had attitude excursions in pitch of plus 10 (degrees) and minus 10, which happened while I was looking out the window making sure that the lateral and horizontal velocities were still nulled."]

[Pete could use the 8-ball to determine the orientation of the spacecraft, but had to look out the window and look for rocks visible through the dust to judge velocities.]

[Conrad, from the 1969 Technical Debrief - "I would allow the attitude of the vehicle to change by plus or minus 10 degree in pitch and not be aware of it, and I had to go back in the cockpit and keep re-leveling the attitude of the vehicle on the 8-ball. I was on the gauges in the cockpit doing that at the time the Lunar Contact light came on. I had that much confidence in the gauges. I was sure we were in a relatively smooth area."]

[The Mission Report gives the time of contact as 110:32:36, which is 06:54:36 UTC on 19 November 1969.]

[Jones - "I gather from the tech debrief that you actually dropped the last two or three feet."]

[Conrad - "You're supposed to."]

[Jones - "And the theory on that was?"]

[Conrad - "Lunar contact light came on and the probes were six feet below the gear. We were supposed to shut the engine off right then because they did worry about the bell mouth too close to the ground."]

[Bean - "Or hitting a rock and denting the bell mouth."]

[Conrad - "And I said, always, 'I'll never do that; who wants to shut off a good engine when you're still in the air?' But we had to train to shut it off. Neil landed with his (engine still) on. And, so, I was going to do the same thing. And, whoever said 'lunar contact light', I went 'bamm' and shut it down. (Laugh) Somewhere in there, I think there's an 'Oh shit'. Or there almost was. But about that time we were on (the Moon), and I didn't have to get it (the 'oh shit') the rest of the way out. I remember that."]

[What Pete is saying is that he intended to keep the engine running until they were down, just as Neil had done. During training, he was a good boy and always shut the engine off immediately after the contact light came on. By the time they were actually landing, shutting the engine off promptly had become so ingrained that he had shut it down before he remembered that he'd wanted to leave it on.]

[Bean - "Probably didn't get the VOX (triggered). Sort of like Neil saying 'A small step' or whatever it is that didn't get out."]

[Armstrong had planned to say 'That's one small step for a man; one giant leap for mankind' but didn't get out the 'a' in front of 'man'. One theory about the omission is that the voice-activated trigger failed to pick up the 'a' and, certainly, at the start of a transmission, the initial syllable is sometimes clipped. However, in Neil's case, the 'a' wasn't proceeded by any noticeable pause and there is no good reason to think that the VOX cut it out. Neil simply mis-spoke.]

[Conrad, from the 1969 Technical Debrief - "I had my head in the cockpit when the Lunar Contact light came on and I instinctively hit the Stop button and that's how we got shut off in the air. We were, I'd estimate, 2 or 3 feet in the air still when I shut down the engine and it dropped right on in. We landed on a slight slope; therefore, the right, plus-Y (north) gear pad touched first and tipped the vehicle to my left. The vehicle plopped on (to the surface) on all four gear at that point, with no skid marks that we could determine (when examining the footpads during the first EVA), other than the first pad touchdown. When we set in for the landing and looked around, it turned out there were more craters around there than we realized, either because we didn't look before the dust started or because the dust obscured them. Now, the landmark visibility (after pitchover) I have to class as excellent. It was very easy from our model and the photographs we had. There was no doubt in my mind when we finally zeroed in at about 6000 feet exactly where I was, that I was in the right place. Had I been short or long, I think it would have been very obvious to me. The lighting was excellent. The surface had a white-gray appearance; the shadows completely black. I was not aware of any washout and I was not aware of seeing zero-phase."]

[The countless small rock particles that make up the lunar regolith reflect a great deal of light back toward the sun because of a process called Coherent Backscatter. If you look toward a point directly opposite the Sun - toward the zero-phase point, you see an extremely bright surface. In addition, if the Sun is low in the eastern sky and you are on the ground, then, in looking toward the west, you can see little detail because rocks and craters hide their own shadows. The result is that the scene looks washed out, with little or no detail discernible. Pete is saying that, at altitude, these effects are less noticeable.]

[Conrad, from the 1969 Technical Debrief - "Everything looked a lot smaller and closer together in the air than it turned out to be on the ground. When we were on the ground, things that were far away looked a lot closer than they really were. The color does change with look angles (relative to the Sun). My yaw (left-right rotation) only changed maybe 10 or 15 degrees in either direction (during the descent). This didn't make too much difference to me in the change of color. (After the landing), whenever we looked directly to our left or right - cross-Sun - things had a browner appearance than normal, which was expected from looking at Neil's photographs. None of these things appeared unusual. I think I might have used the LPD more, closer in, but I was sure that we were so much on target that I really didn't need it. That may have caused my slight overflying and taking over to stop what I thought was a relatively high horizontal velocity. As it turned out, I don't think we landed more than 400 feet from the Surveyor."]

[During the next several minutes, Pete and Al will shut down the Descent Stage and prepare the Ascent Stage for an immediate departure on the off-chance that one will be necessary. Unlike the Apollo 11 crew, they will not go through a simulated countdown and, once they and Houston are satisfied that the LM is in good shape, they will prepare the vehicle for the planned 32-hour stay.]

[Conrad - "That's one of those shut-off valves for the helium pressure."]

[Jones - "And 'recycle'?"]

[Conrad - "We probably cycled them to make sure they were off."]

[Pete is mistaken. The valves were supposed to be open, so cycling them meant setting the switch to close and then back to open.
[Frank O'Brien - "A recurring problem in the Apollo program was that the RCS propellant isolation valves - essentially, shut-off valves - occasionally closed during periods of heavy vibration or shock (such as during a landing), rendering that particular RCS thruster unusable. Because the Service Module and Lunar Module used similar components, the valves in the RCS systems of both spacecraft could be affected by this. Indeed, starting with Apollo 12, one of the first post-landing steps for the Lunar Module was to cycle these valves to ensure they were open. Fortunately, this problem usually was regarded as a nuisance, since it was easily remedied."]

[In 1999, Journal Contributor Neville Kidger notes that the valves were made by a U.S. unit of his employer, Parker Hannifin PLC. "Al Bean first referred to cycling a Parker valve on Apollo 12 just after touchdown and at least one of our employees, Anthony Tonge, remembers that from the real time audio!"]

[Jones - "So you had a minute to get the descent stage shut down and the ascent ready to go?"]

[Bean - "We had to be ready for an abort, a no-stay from the ground. First, we had to safe things; and then we had to be ready in case they said you got a no-go. So we were trying to get configured, I think, here, if we had to abort."]

[Jones - "The stay for T1 comes down here at 110:34:44, which is just a minute from now."]

[Bean - "That's right. So that's why we were in a big hurry. 'Cause if they hadn't (given the stay), we had to have done this correctly. As I recall. Can't figure out why we would be in a hurry otherwise. We'd done the hard part. Pete did the hard part, and we're just shuffling paper (checklists), here."]

[Jones - "Did you do this part in the sims a lot?"]

[Bean - "Oh, yeah. You would have to abort sometimes. They'd call up and say you were leaking."]

[During training, Pete and the other commanders flew the Lunar Landing Training Vehicle, or LLTV - and a similar, predecessor called the Lunar Landing Reserach Vehicle or LLRV - and, of course, 'flew' numerous landing simulations in immobile simulators on the ground. The LLRV/LLTV - or The Flying Bedstead, as it was sometimes called - was built for NASA by Bell Aerosystems, Buffalo, NY and consisted of an open frame that supported a large, down-pointing jet engine that removed 5/6th of the effective vehicle weight and allowed the pilot then to use the equivalent of the Descent engine and RCS thrusters to practice landings. The accompanying photo shows Pete flying the LLTV.]

[I asked Pete about the value of this training.]

[Conrad - "I think everybody agreed that the LLTV was very essential to a successful landing. One of the problems which we were talking about earlier at lunch is that you have to realize that the visual on the simulator was very bad. We had a plaster-of-paris lunar surface (called the L&A) and a B&W television camera (that flew to it). So you're looking at a flat, no-depth boob tube - a television - in the window. So, the last five hundred feet, if you were watching that out the window in the simulator, it wasn't any good. It just didn't really resemble the real world."]

[Bean - "It was a virtual image something or other. Which was a flat TV with some optics that..."]

[Conrad - "Tried to give it depth..."]

[Bean - "But it didn't."]

[Conrad - "It was the best they had at the time. We didn't have a moving-base simulator, either. (In more recent times, Shuttle crews have been able to train in simulators that move in response to crew inputs and, thereby, give much more realistic simulations.) So, the LLTV was critical, to get a real feel. And the reason Al made the comment about maneuvering at 110:31:06 is that the LMPs didn't fly the LLTV."]

[NASA built two LLRVs and three LLTVs. Three of these five vehicles were lost in accidents. Because of the jet engine, the LLTV was actually a less stable vehicle than the LM and, therefore, was harder to fly. For this and other reasons, it was decided that only people who absolutely needed the experience - mission commanders and their backups - would fly the LLTV. None of the LMPs ever flew one.]

[Conrad - "By the time I flew, Neil had jumped out of one LLTV (May 6, 1968) and at least one of our Ops pilots bailed out. (Actually two non-astronaut test pilots, Joe S. Algranti and Stuart M. Present, bailed out, on December 8, 1968 and January 29, 1971, respectively). (NASA Administrator) Dr. Gilruth, bless his soul, just worried to death that somebody was going to get bagged in an LLTV. And so, he asked everybody when they came back (from the Moon) 'Do you think it's necessary to fly the LLTV?' And, the feeling that I think Neil had and myself - and I'm quite sure the rest of the guys - was 'Yes, you really should go ahead and fly the LLTV.' But, having had the three accidents and having that one vehicle left, Dr. Gilruth asked the guys to figure out how many flights we got on a vehicle before we crumped one. And it turned out to be like 260 flights or something like that. To finish the training after the third accident, they had to fly 240 more flights; and, so, when Gene (Cernan, the Apollo 17 Commander) flew the last flight in his training, the thing went to the Smithsonian or whatever because nobody was ever going to fly that thing again as far as Gilruth was concerned. And he almost didn't authorize the training, see. And so, at least the early guys pushed very hard for everybody to continue flying it."]

[Bean - "I remember you talking about it when they asked you. And really pushing hard for it."]

[Conrad - "Al hadn't flown one, and that's why he made the remark (110:31:06) when I started really maneuvering the thing around. Because you had big attitude changes up there, because you're in a low gravity field. He had seen that kind of a maneuver, probably, inside the simulator. But that virtual image display and the fixed base didn't really give you any feel for it. So, the first time Al really experienced that was at the Moon. And I just passed it off 'Yeah, I'm busy doing what I was doing.'!"]

[Bean - "We were all flying helicopters and you didn't maneuver a helicopter any where near like that. Up there, you really had to move the LM to maneuver it. So Pete got used to it and I was thinking helicopter kind of stuff. So, when you (Pete) suddenly maneuvered much more than a helicopter, it caught me by surprise. But to you, well, that's the way you do it. I think it's because, on Earth, you're supporting the weight with a certain amount of thrust. So, let's say you've got to knock off ten foot per second forward. You pitch up (means tilt the LM back and, therefore, the direction of thrust up) to a certain angle to do that and you get used to that kind of maneuver. You go on to the Moon; you've got one sixth the thrust to hold this same mass up and ten feet per second forward with that mass is the same as it was on Earth. But, in order to stop it (meaning slow it down by ten feet per second) with one-sixth the thrust, you're going to have to pitch up (means tilt the LM back) a lot harder. So I think it's just strictly the fact that you're operating with less thrust than a helicopter for the same weight and the same momentum. So, in order to use it, you've got to get that thrust vector up higher faster or you're just never going to slow down the translations - or get one going and then stop it. When you think about it, it makes sense. But, at the time, it just seemed like 'God, what's he doing?' It felt to me like you were pitched too far (back), you know. And you probably were doing quite a bit because you've got to get it (pitched) up there to get the little ol' thrust vector to work."]

[Conrad - "That's right, you have to move it more to get the maneuver. So it looks really bad to you, although nothing serious is happening."]

[Bean - "It looked normal to you!"]

[Conrad, from the 1969 Technical Debrief - "I think the manual control of the LM was excellent. The LLTV is an excellent training vehicle for the final phases. I think it's almost essential. I feel it really gave me the confidence that I needed. I think the (immobile) simulator did an excellent job in manual control and LPD training all the way down to the last couple of hundred feet. I think both devices worked very well together."]

110:34:09 Conrad: Boy, am I glad I was high, Al, I couldn't...

110:34:10 Carr: Roger, Pete.

110:34:11 Bean: I know it. Holy cran, it's beautiful out here!

['Holy cran' obviously is a mild oath; but it is not one I've ever heard elsewhere.]

110:35:11 Conrad: Hey, we flew right by the crater, Houston, but this ground (to the west of the LM) looks neat out here. We're not going to have any trouble going back there (to Surveyor Crater).

110:35:16 Carr: Roger.

[Conrad - "It's not 'til I get outside (starts laughing) that I realize I was sitting right on the side of the crater. I'd thought I'd gone a little bit past it."]

110:35:18 Bean: Okay. We're in lunar alignment, Houston, with the AGS. Let me know when you get to (P)68 and I'll write down (lost under Carr)

110:35:21 Carr: Where'd you put her down, Pete; over on site 4?

110:35:27 Conrad: No, sir. About halfway between site 4 and site 3. I flew by the right (north) side of the (Surveyor) crater and then had to fly over to the left and land. We're in good shape.

110:35:40 Carr: Roger.

[As can be seen in version of map 7-F as re-drafted by Thomas Schwagmeier, Site 3 is about 210 meters north and slightly west of the actual landing site and Site 4 is about 500 meters southwest. Site 4 is about 70 meters southwest of Sharp Crater. A point halfway between would put him just west of Head Crater rather than on the northwest rim of Surveyor Crater. However, we must be wary of making any firm conclusion about where Pete thought he was until the moment when he finally realizes that Head Crater is well out in front of him and that Surveyor Crater is right behind him. At several points during the discussion with Houston, Pete mentions flying past the north side of Surveyor crater and then going a little left to land. This is what he actually did. What may be confusing him is the fact that he hasn't recognized Head. This could be making him think he's west of Head. However, those inclined to further speculation should note that he never specifically says he's west of Head.]

[Jones - "You haven't seen the Head (and won't until 112:39:45). You don't realize that the Head's out in front of you. Because of the low sun angle."]

[Conrad - "I think you're right. I think we didn't realize that there's a (guffaws) big crater sitting right in front of us."]

[Bean - "Ohh! I always thought you thought you landed near the (Surveyor) crater."]

[Conrad - "So did I. Until right now." (Uproarious laughter)]

110:35:41 Bean: Reset your engine stop, Pete.

110:35:42 Conrad: Okay.

110:35:44 Bean: You made a beautiful landing.

110:35:45 Conrad: (To Houston) You guys did outstanding targeting! I'll tell you, that thing was right down the middle. Beautiful!

[Bean - "The geologists wanted us to get bedrock, if we could. I remember we were supposed to find boulders. And we saw these way out there and we were thinking, 'Boy, we'll go get 'em.' And they turned out to be..."]

[Conrad - (Laughing) "Maybe five miles away!"]

[Bean - "Three miles away or something. We thought they were right over there, didn't we? I thought they were a hundred yards, two hundred yards, maybe. They were shining from that light behind us. They were real white-looking rocks."]

[The boulders in question are probably associated with a 500-meter-diameter crater that is 4.5 kilometers or nearly 3 miles west of them.]

[Frames AS12-48-7023 to
7033 are a post-landing, pre-EVA window pan of the site. The large crater on the horizon is best shown in
7024. Figure
10-13 from the Apollo 12 Preliminary Science Report shows where Bench, Head, and Middle Crescent Craters can be found in these pictures.]

110:39:09 Bean: Those rocks...Are we on the Copernicus Ray area? (Pause)

110:39:16 Conrad: Is that right? Oh, great! (Pause)

[In Ulli Lotzmann's annotated telescopic view of the landing site, Copernicus is the large, rayed crater north of the yellow box. In a combined version of lunar surface maps LSM_7-AG and BG, the western boundary of a Copernicus Ray has been highlighted and a box has been drawn around the Snowman. A detail from LSM_7-AG shows the ray boundary as a dashed lined with smaller lines (hachures) pointing generally to the right (east) toward the interior of the ray. See, also, Figure 2 and its legend in section D of the Apollo 16 Professional Paper.]

110:39:28 Bean: We'll get it (the map) out.

110:39:31 Conrad: Okay, Houston. Are we Go or Stay?

110:39:34 Carr: Intrepid, Houston. You're Stay; and if you'd like to recycle and try it again, we'll talk to Sims.

[During training, they flew the landing repeatedly and Carr is asking if they would like to have the simulation team set up for another try.]

110:39:41 LM Crew: (Laughing) No.

110:39:42 Conrad: No, not this time.

110:39:43 Bean: Yeah. We're still mad at him (meaning the head of the simulations team) for earlier in the week.

110:39:48 Carr: Roger.

[Conrad - (Laughing) "Here we go again! We're still mad at him."]

[I asked them to explain.]

[Conrad - "That's about the lightning strike (during the launch). (Laughing) We told them that that beat all the sims to hell."]

[Bean - "That's right."]

[Conrad - "Which it did."]

[During the launch, the Apollo 12 Saturn V passed through some rain cloud and, in hindsight, the plume of partially ionized gas created by the exhaust formed a perfect lightning channel. When the cloud discharged, all of the circuit breakers in the Command Module tripped and, although the Saturn V was unaffected and continued calmly on its way, the effect on the startled crew was 'electric'. The lightning discharge also struck the launch pad.]

110:39:50 Bean: Okay. Let's get off VOX (voice activated comm).

[They will switch to the Push-to-Talk (PTT) comm mode, pressing a button whenever they want to talk to Houston. In PTT they will sometimes push the button accidentally or out of habit and such communications are indicated by 'Unintentional key'.]

[Bean - "It's probably what pressurized the descent stage tanks. I think we just let off the helium and the fuel (and oxidizer) stayed inside."]

[Conrad - "That stuff was hypergol(ic)s (which would ignite on contact with each other) and I don't believe we vented the hypergols. What we did was just dropped the pressure in the tanks by venting all of the helium overboard. I want to remember that it didn't vent as fast as in the simulator or something."]

[Bean - "You're right. It wasn't venting (very fast). In the simulator, after a little while it was gone. And in this thing..."]

[Conrad - "It took a long time."]

[Bean - "That's right. It just stayed up and that's why you're asking about it."]

[Conrad - "Because helium was the hardest stuff in the world to contain; and it turns out, when we wanted to get rid of it, we weren't getting rid of it very fast."]

[Bean - "It's just picky. It just won't cooperate."]

110:41:04 Conrad: Okay; I'll tell you what. We're going to start hustling along here, so I'd appreciate it if you'd give me a holler when it gets down in the 2 to 8 (psi) range.

110:41:15 Carr: Will do it, Pete. (Long Pause) Intrepid; Houston. You can close your ox(idizer) vent. Leave the fuel open for a little while.